1. Introduction
Ensuring access to affordable, reliable, sustainable, and modern energy is the aim of UN Sustainable Development Goal (UN-SDG) 7, which is also critical to improving livelihoods and fighting against poverty for billions of people around the world. In 2019, over 840 million people remained without access to electricity. Nearly three billion people still lacked clean cooking fuels as well as technologies [
1], forcing them to rely on traditional biomass fuels (e.g., crop waste, dung, wood, etc.) for daily energy needs. Most such populations live in rural areas of the developing world, mainly distributed in low-income and lower-middle-income countries, especially in Sub-Saharan Africa and Southeast Asia [
2]. These regions often face a similar dilemma: Weak infrastructure and low-income levels make clean energy neither available nor affordable, which, in turn, reinforces the persistence of poverty.
The primary use of energy in households in developing countries is for cooking, followed by heating and lighting. Because of geography and climate, household heating needs are minor in Sub-Saharan Africa and Southeast Asia [
3], whereas cooking is the most fuel-intensive activity. Cooking begins with the process of interaction between fuels and stoves. The lack of access to clean cooking fuels forces poor people to rely on inefficient and polluting cooking systems [
4], in which solid fuels (biomass, wood, and coal) are often not fully burned. Such use of low-quality fuels leads to several sustainability challenges: (1) A labour challenge because of the time-consuming collection of biomass [
5]; (2) deforestation and land degradation; and (3) most importantly, the indoor exposure to harmful gases and particles. The World Health Organization (WHO) has determined that the typical 24-h indoor PM10 (particulate matter 10 micrometres or less in diameter) concentration can reach 300 to 3000 μg/m
3 in residences using biomass in Africa, Asia, and Latin America, while the peak PM10 concentration during cooking can even reach up to 10,000 μg/m
3 [
6]. The continuous use of solid fuels will increase the level of indoor air pollution, leading to issues such as respiratory tract infections, heart disease, tuberculosis, low birth weight, cataracts, cardiovascular events, higher adult mortality, and risks of premature death [
7,
8]. According to the International Energy Agency (IEA), household air pollution, mostly from cooking smoke, is linked to around 2.5 million premature deaths annually [
2], which adds a burden on national health systems attributable to household air pollution [
9], and further restricts the social and economic development of such countries.
Achieving clean cooking needs a replacement of polluting stoves and fuels with cleaner alternatives, such as cooking with Liquefied Petroleum Gas (LPG) or electricity, which has been widely analysed in empirical studies [
10,
11,
12,
13,
14,
15]. However, rural areas are usually remote in many lower-income countries with relatively weak infrastructure, and people living there often find it difficult to access modern energy services [
16]. LPG needs specialised transportation, storage, and distribution [
17], which requires the construction and maintenance of roads. Many areas have also performed experiments exploring the feasibility of cooking by electricity―i.e., utilising induction stoves given their higher efficiency and lower power consumption than electric coil stoves [
4]. Still, these were not as welcomed as expected [
18,
19]. For people living in electrified areas, the additional electricity bills generated by cooking may be a significant burden to their family, thus forcing them to remain on multiple fuel combinations, like biomass [
20,
21,
22]. Because the average cost of grid connections increases with distance [
23], the extension of the grid to specific rural locations may be considered uneconomic and inefficient because of the scattered living conditions and significant transmission losses [
24,
25,
26]. There are evidences that subsidies from the government are effective in encouraging the use of clean fuels, but they might not be financially sustainable [
21,
27]. All of these obstacles for poor people to achieve clean cooking by LPG or electricity demonstrate the great significance of the long-term accessibility and affordability of clean fuels from the perspectives of both the government and households.
The technical progress in utilising renewable energies, especially off-grid distributed renewable energy systems, offers potential alternatives to grid electricity [
25]. The Solar Home System (SHS) is one of the most promising household renewable energy suppliers, generating electricity with no air pollution or carbon emission. A basic SHS includes a photovoltaic (PV) solar panel, a battery for electricity storage, and a battery charging controller used to employ power for various end-use devices (such as fluorescent lights) [
28]. In the early days of SHS, it primarily supplied complementary clean electricity to replace pollutant fuels for some low-power energy services, such as replacing kerosene for lighting in low-income countries [
29]. Cases in Ghana [
30], Bangladesh [
24], Sri Lanka [
31], Indonesia [
32], and Kenya [
33] have illustrated that the large-scale penetration of SHS could effectively help rural communities both in terms of alleviating energy poverty and reducing adverse environmental impacts, such as indoor air pollution. Recently, as the PV production and technology have developed greatly, costs of solar power have fallen dramatically and will fall further [
34]. A case study in Sub-Saharan Africa reinforced that the cost of PV power generation within its lifecycle could drop to
$0.10/kWh, and even
$0.03/kWh if aggressive cost declines in PV batteries were realised. This suggests that the decentralised solar power system and centralised power grid could potentially realise basic parity in cost [
35], indicating that SHS has the potential to power more household appliances. Although the initial investment for an SHS is still relatively high even with the falling price of PV panels, it is capable of paying back the initial investment within the first several years of operation through savings in electricity bills [
23,
24,
29]. The most remarkable benefit of SHS is that once installed, the marginal cost of generation is zero [
36], effectively encouraging people to use it. Therefore, many low-income and lower-middle-income countries have been making efforts to deploy renewable solar energy as part of wider electrification programs in rural areas [
37].
Traditional sources of clean fuels (LPG and grid electricity) have either accessibility challenges or affordability deficiencies in lower-middle-income countries (LMCs). Due to the potential for off-grid distributed renewable energy systems, this study proposes using SHS as the clean energy supplier for clean cooking. We thus aim to answer whether areas with energy access problems can achieve clean cooking by: (1) To cleaner cooking units utilising induction cooking stoves (ICS); and (2) to cleaner cooking fuels for such ICS utilising distributive SHS. We then proceed with a cost–health benefits analysis to estimate the cost of upgrading to this portfolio and compare the cost with the monetised health losses from indoor air pollution. The results should provide new thoughts for policymakers and other interest groups to solve the energy access problem as well as clean cooking at the same time.
4. Discussion
4.1. Uncertainties of Cost
From the results, we can see a significant gap between the minimum and the maximum costs for the ICS-SHS portfolio. The cost calculations are subject to considerable uncertainties, especially the cost of SHS. For example, the price of PV modules, balance of system (BOS), and installation costs may vary largely in different countries, while the total cost is highly dependent on the price of PV modules. In this study, the costs of BOS and installation are estimated according to the fixed ratio to the PV modules given local data unavailability. This analysis also uses the national GHI to estimate yearly electricity generation, without taking into account the factors like rainy days, SHS transmission loss, etc. Besides, the GHI is the average level across a country, regardless of regional differences. Each individual datum has its uncertainty, which leads to more significant uncertainty when these data are calculated together. However, this analysis aims to provide a rough range of the cost, as well as offering references for those interested in clean cooking, such as households, sponsors, and policy makers.
4.2. Financial Options to Support SHS
It is worth noting that in the poorer LMCs in Southeast Asia, such as Laos, Vietnam, Cambodia, and Myanmar, although households in these countries have the most severe clean cooking access problems, the estimated health benefits they can obtain from upgrading to ICS-SHS are smaller and much closer to the estimated minimum cost of the upgrade. Given the benefits that upgrading to clean cooking may bring, in practice, however, renewable power generation is historically characterised by high initial capital [
58]. Although the upgrade to ICS-SHS is most needed in these countries, given the estimated relatively minor gap between the health benefits and cost, it may prove difficult to persuade these households with limited payment ability to invest in ICS-SHS. The question of whether this portfolio could be used as a solution to clean cooking also depends on how and who to pay for an SHS when it is beyond the direct beneficiaries’ affordability, and who might help bear such costs.
4.2.1. Public Policies and Finance
The universal access to clean energy through innovative public-private partnerships is possible, but will initially require substantial investments in capacity development and market-motivating policies. Public funds can account for a significant proportion of the total cost of decentralised energy investments, especially in the early stages [
59]. Rural electrification is not generally considered a lucrative market, especially in developing countries [
60]. It therefore requires the promotion and input from the government. In terms of public policy frameworks, the most powerful incentives for developing countries to deploy renewable energy are clear national targets for renewable energy [
61]. A review of 17 energy access initiatives for the poor in the Asia-Pacific region by the United Nations Development Program (UNDP) concluded that countries that were able to achieve significant expansion benefited from the strong commitment reflected in policy documents and supported by budgetary allocations of their national governments [
62]. Uncertainty about whether governments would continue to provide financial support for specific clean energy opportunities might discourage investors from investing or require higher returns to compensate for this risk [
63]. Therefore, the government should consider setting national goals for the development of renewable energy, making full use of public policy tools, and providing more fiscal resources in order to improve the feasibility of rural electrification.
Appropriate subsidies are crucial, although the subsidies themselves do not necessarily guarantee the success of the project. For example, the terms and conditions of rural electrification projects often do not align with commercial loans [
64]. Poor rural residents may be unable to obtain loans without collateral or guarantors, etc. In rural areas, income usually depends upon the harvest or other irregular activities, and more flexible payment times may therefore be required [
65]. At this point, the government needs to step in and provide financing channels or subsidies to commercial banks or private enterprises that provide loans or instalment payments for the SHS project in order to encourage such development in the rural energy sector. The eventual policies may be likely to be a basket, containing tax and tariff elimination on clean energy installations [
66], subsidy reduction on fossil fuels, and promotion of income-generating activities for end-users of SHS services [
67].
4.2.2. Market-Driven Finance
There are two main financial models for large-scale development of rural electrification: Pay-for-service models and microcredit schemes.
One problem for SHS users in remote rural areas is the lack of maintenance services. The pay-for-service model, first adopted in the Pacific region, is one in which energy companies remain the owners of installed equipment and, if necessary, are responsible for maintenance or repair (for a fee) [
68]. As remote residents have limited access to technical resources and bank loans, the pay-for-service model is realistic for overcoming such obstacles in rural electrification by SHS.
Many rural SHS financing projects based on microfinance institutions have successfully expanded rural electrification, primarily in South Asian countries, such as Sri Lanka, Bangladesh, and India [
69]. Currently, the innovative microfinance model Pay-As-You-Go (PAYG) has become one of the most commercially viable solutions to provide decentralised energy to rural and remote communities in developing countries. Household affordability is a key challenge for energy companies, and PAYG’s simple payment scheme makes solar power affordable and allows households to gradually own these systems [
70]. The PAYG model also provides user training, ongoing maintenance, and minimisation of investment risk. PAYG has seen enormous success in Sub-Saharan Africa, and Kenya has pioneered this model as a cost-competitive modern alternative to kerosene. With modern information technology and mobile connectivity, PAYG can offer online payments flexibly, making the system more affordable. The ability to remotely block SHS without payment reduces the transaction cost of collection and investment risks for microfinance companies [
71].
4.2.3. Non-Governmental Finance
Since the 1990s, the World Bank has recognised that SHS can contribute to rural electrification. For the past 20 years, the World Bank and Global Environment Facility (GEF) have approved 12 SHS projects to provide basic energy services, such as lighting, broadcasting, television and the operation of small electrical appliances, to rural households that cannot be connected to the grid [
72].
The Dutch Development Organization (SNV), a non-profit international development organisation from the Netherlands, has implemented a technical assistance program in Cambodia aimed at promoting the development of a sustainable off-grid solar industry locally to improve access to energy for rural households, which is the largest domestic solar market development to date. By September 2016, 1387 rural households had purchased certified solar products from one of six certified solar suppliers. Fourteen of Cambodia’s 25 provinces had provided high-quality products and related customer services. Half of those sales used one of 687 solar loans, totaling 355,524 USD, from four microfinance partners. The implementation of the first 12 awareness-raising campaigns helped educate some 12,000 rural Cambodians. Generally, governmental and non-governmental organisations have been playing an essential role in rural electrification [
73,
74].
4.3. Limitations of SHS
Admittedly, SHS is a clean household energy supplier with great potential, especially as the price of PV panels has kept declining in recent years. There are several reasons that SHS has not been as popular as expected even with several financing modes in developing countries. Firstly, solar energy is an intermittent energy source susceptible to weather, implying its weaker reliability than grid electricity. As SHS cannot generate electricity at night or on cloudy days, batteries are thus needed for energy storage. If a household relies solely on SHS to electrify their home, there may be insufficient power at night and in the rainy season. While energy storage batteries help reduce load and stabilise the system, they also push costs up further. Secondly, the substantial upfront cost has always been a disadvantage hindering SHS. Although the cost–health benefit analysis in this study proves that the health benefits brought by the adoption of SHS are far higher than the investment in the long run, the initial cost may be a real obstacle for poor people; after all, health is something that can be squandered in the future. This is why this study has emphasised the diversification of financing models. However, considering that many countries still provide subsidies for the consumption of traditional energy, a further challenge to SHS will be the chronically low prices of fossil fuels, which may push back its ability to compete.
4.4. Long-Term Motivations
Regarding the health benefit assessment, every family in these six countries can enjoy significant health benefits during the year from upgrading to clean cooking. The reduction of cooking-attributable indoor air pollution may be directly reflected in fewer illnesses and lower medical expenses. In the long term, improving indoor air quality will bring better health conditions and longer lives for whole families, especially women and children who spend longer times indoors and are thus more vulnerable to indoor air pollution [
5]. In particular, the investment is basically one-off, while the health benefits will exist throughout the entire utilisation of ICS-SHS, which makes the portfolio more attractive to motivate the willingness to pay.
Meanwhile, SHS provides clean energy access to unelectrified households, the impacts of which will not be limited to replacing fuel itself, but also diffuse to the equality, opportunity, and future of these households. For instance, women and children are almost always responsible for household fuel collection in undeveloped countries, given their lack of educational opportunities and inability to generate income. However, with available clean energy, women can devote time to other productive activities with higher returns, and children can have more time for education [
75]. Although the power generation of the SHS in this study was designed for induction stoves, the excess power can be stored in a battery and used in other appliances. Electricity brings more possibilities for people to enjoy modern conveniences, which are also helpful in lifting poor people out of poverty.
5. Conclusions
This study proposes that renewable solar energy be employed to supply power for induction cooking stoves (ICS) through solar home systems (SHS), thereby realising clean cooking, improving indoor air quality, and solving the energy access problem simultaneously.
Based upon data availability and proximity, this analysis selected lower-middle-income countries in Southeast Asia (Indonesia, Philippines, Lao PDR, Vietnam, Cambodia, Myanmar) as the research targets for conducting a cost–health benefit analysis of such an approach, estimating both the costs and health benefits of upgrading to ICS and SHS. In the analysis, the cost of upgrading to the ICS-SHS mainly consists of the cost of an ICS, an SHS, and cookware. The Disability-Adjusted Life Years (DALYs) and the value of a statistical life year (VSLY) were calculated to estimate the health benefits. The results suggest that the health benefits brought by ICS-SHS alone can at least surpass the estimated minimum cost for an ICS-SHS in the six LMCs in Southeast Asia. Although the relatively high initial cost of an SHS tends to be an obstacle in its popularisation, there are financial supports available from governments, international organisations, non-governmental organisations, and private companies that have multiple experiences in solely or jointly funding the installation and operation of SHSs in rural areas. These cases have enlightened late-comers to pay attention to the motivation from national strategies, the cooperation within different institutions, demand-creating, and relevant risks. This study thus reveals the feasibility of ICS-SHS in achieving clean cooking and addressing indoor air pollution as well as energy access problems in the six LMCs of Southeast Asia, providing a reference for other countries facing similar problems.